The present invention is directed to polyalkylene carbonate terpolymers which are easily melt processed without extensive thermal degradation.
Polyalkylene carbonates are well known in the art and are easily prepared using a variety of catalysts. Epoxides are known to copolymerize with carbon dioxide, with metal containing catalysts such as zinc diethyl and additives, zinc dicarboxylates, and aluminum porphyrin complexes.
The resulting copolymers have alternating epoxide and carbon dioxide groups, and are polycarbonates. These copolymers have found uses in many areas, such as thermoplastic applications including injection molding, blow molding and film manufacture, ceramic binders, evaporative pattern casting and adhesives. Epoxides shown to proceed readily in this reaction are ethylene oxide, propylene oxide, cyclohexene oxide, cyclopentene oxide, isobutylene oxide, cis-2-butene oxide, and others.
Polyalkylene carbonates, essentially 1:1 molar ratio copolymers between epoxides and carbon dioxide, have many thermoplastic applications which require the polymers to be exposed to heat treatment during melt processing, compounding or modification. Although a simple polypropylene carbonate is not too unstable thermally, it is desirable to make certain modifications rendering it more thermally stable for the purpose of melt processing. Polypropylene carbonate can be melt processed but during processing significant decomposition occurs even in the presence of various stabilizer packages and antioxidants. Decomposition to propylene carbonate monomer occurs by unzipping mechanisms and carbonate linkage scission via hydrolysis readily occur to diminish the properties of the products made during processing. Another desirable feature of the invention would be to increase the temperature window in which the polymer has reasonable melt viscosity to give thermoplastic flow with no significant degradation, thus increasing the processing flexibility of the polymer.